The present invention relates to ultrasonic measurement systems, for example systems such as are used to determine properties of a fluid flowing within a conduit. These systems operate by creating an ultrasonic signal burst, and transmitting the burst into the fluid and receiving the signal after it has traveled along a path through the fluid. Two or more related paths may be used (for example upstream and downstream paths, orthogonal paths, or clockwise and counterclockwise paths) to develop signals indicative of sound speed, or of directional differences in sound speed that depend on flow components. Generally the property of the fluid is determined as a function of the transit times of these signals.
Often it is desired to obtain from the signals useful information such as the mass flow rate, or the caloric value of the material flowing in the conduit. In that case further information is necessary and this often requires the system to operate in controlled environments where the user enters extrinsic data via a keyboard to specify the known components of material in the flow so that the signal processor can perform its calculations with the corresponding values of physical parameters for those materials. However, such operation is only possible in a limited number of well controlled circumstances. In some plants, and especially in situations where flue gases are present, the composition of the gas stream will vary over time. It may also be subject to certain fast fluctuations, as occurs in flare gases or certain hydrocarbon processing environments. When the gases present under these measurement conditions are used in bulk processes involving hydrocarbons, the monetary value of material flowing in the conduit can be substantial, and it may be necessary to know its volume and composition with relatively high accuracy for processing, control or environmental reasons.
It would therefore be desirable to extend the useful operating conditions of ultrasonic measurement systems to include flows with varying but unknown composition of hydrocarbon components.
It would also be desirable to provide an ultrasonic measurement system which determines the molecular weight of a component of a fluid flow.